title: A new method to determine biological sample volume by short end multiple injection capillary electrophoresis: application in determination of nitrate and thiocyanate in human saliva.
abstract: The aim of this study was to develop a simple and rapid method of capillary electrophoresis using a short end multiple injection in free solution to determine simultaneously the biological sample volume and analytes concentration. The method consists of a sequence of injection steps with an internal standard as the reference for correction of the volume of sample collected. The procedure was applies in the determination of NO(3)(-) and SCN in saliva samples. The background electrolyte was composed of 12 mM tris(hydroxymethyl)aminomethane and 8.5mM sulfuric acid, at pH 2.5. The internal standard used was BrO(3)(-). A fused silica capillary (48.5 cm total length, 8.5 cm effective length and 75 μm i.d.) coated with chitosan was used in a short-end injection configuration. Modification of the electroosmotic flow (EOF) using dynamic coating resulted in a controlled and stable EOF, contributing to the rapid separation of anions (0.36 min) in co-electroosmotic mode. The validation of the method for correcting the volume of saliva collected with a swab showed a difference of less than 3.5% compared with the predicted value and a correlation of 0.999. The limits of detection for NO(3)(-) and SCN(-) were 0.13 and 0.23 mg L(-1), respectively. The inter-day precision of the method determined for both analytes was less than 5% and the recovery ranged between 97 and 102%.
authors.affiliation: Department of Chemistry, Federal University of Santa Catarina, Campus Universitário Trindade, 88040-900 Florianopolis, SC, Brazil.
authors.forename: Luciano
authors.initials: L
authors.lastname: Vitali
authors.forename: Valfredo T
authors.initials: VT
authors.lastname: Fávere
authors.forename: Gustavo A
authors.initials: GA
authors.lastname: Micke
mesh_terms: D019075:Electrophoresis, Capillary / Q000379:methods*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D009566:Nitrates / Q000032:analysis*; D015203:Reproducibility of Results; D012463:Saliva / Q000737:chemistry*; D012680:Sensitivity and Specificity; D013464:Sulfuric Acids; D013861:Thiocyanates / Q000032:analysis*
chemical_list: D009566:Nitrates; D013464:Sulfuric Acids; D013861:Thiocyanates; C033158:sulfuric acid; C031760:thiocyanate